Cable television networks such as those provided by Comcast Cable Communications, Inc., of Philadelphia, Pa., Cox Communications of Atlanta Ga., Time-Warner Cable, of Marietta Ga., Continental Cablevision, Inc., of Boston Mass., and others, provide cable television services to a large number of subscribers over a large geographical area.
The cable television networks typically are interconnected by cables such as coaxial cables or a Hybrid Fiber/Coaxial (“HFC”) cable system which have data rates of about 10 Mega-bits-per-second (“Mbps”) to 30+ Mbps.
The Internet, a world-wide-network of interconnected computers, provides multi-media content including audio, video, graphics and text that requires a large bandwidth for downloading and viewing. Most Internet Service Providers (“ISPs”) allow customers to connect to the Internet via a serial telephone line from a Public Switched Telephone Network (“PSTN”) at data rates including 14,400 bps, 28,800 bps, 33,600 bps, 56,000 bps and others that are much slower than the about 10 Mbps to 30+ Mbps available on a coaxial cable or HFC cable system on a cable television network.
With the explosive growth of the Internet, many customers have desired to use the larger bandwidth of a cable television network to connect to the Internet and other computer networks. Cable modems, such as those provided by 3Com Corporation of Santa Clara, Calif., Motorola Corporation of Arlington Heights, Ill., Cisco Corporation of San Jose, Calif., Scientific-Atlanta, of Norcross, Ga., and others, offer customers higher-speed connectivity to the Internet, an intranet, Local Area Networks (“LANs”) and other computer networks via cable television networks. These cable modems currently support a data connection to the Internet and other computer networks via a cable television network with a data rate of up to 30+ Mbps, which is a much larger data rate than can be supported by a modem used over a serial telephone line.
Many cable television networks provide bi-directional cable systems, in which data is sent “downstream”, from a “headend” to a customer, as well as “upstream”, from the customer back to the headend. The cable system headend is a central location in the cable television network and, further, is responsible for sending cable signals in the downstream direction and receiving cable signals in the upstream direction. An exemplary data-over-cable system with RF return typically includes customer premises equipment entities such a customer computer, a cable modem, a cable modem termination system, a cable television network, and a data network such as the Internet.
Some cable television networks provide only uni-directional cable systems, supporting only a “downstream” data path, which provides a path for flow of data from a cable system headend to a customer. A return data path via a telephone network, such as a public switched telephone network provided by AT&T and others, (i.e., a “telephone return”) is typically used for an “upstream” data path, which provides a path for flow of data from the customer back to the cable system headend. A cable television system with an upstream connection to a telephone network is typically called a “data-over-cable system with telephony return.”
An exemplary data-over-cable system with a telephony return typically includes customer premise equipment (“CPE”) entities (such as a customer computer or a Voice over Internet Protocol (“VoIP”) device), a cable modem, a cable modem termination system, a cable television network, a public switched telephone network, a telephone remote access concentrator, and a data network (e.g., the Internet). The cable modem termination system and the telephone remote access concentrator combined are called a telephone return termination system.
If the customer premises equipment entity comprises a telephone or a device capable of sending and receiving video or voice signals, the cable modem has to be capable of sending and receiving such signals. In such cases, the cable modem typically comprises an internal media terminal adapter, which provides a network interface functionality that accepts analog voice inputs or video signal and generates IP packets using the Real Time Transport Protocol, for instance.
In a bi-directional cable system, when a cable modem termination system receives data packets from a data network, the cable modem termination system transmits received data packets downstream via the cable television network to a cable modem attached to a customer premises equipment entity. The customer premises equipment entity sends response data packets to the cable modem, which sends the response data packets upstream via the cable network. The cable modem termination system sends the response data packets back to the appropriate host on the data network.
In the case of a telephony return system, when a cable modem termination system receives data packets from a data network, the cable modem termination system transmits the received data packets downstream via a cable television network to a cable modem attached to a customer premises equipment entity. The customer premises equipment entity sends response data packets to the cable modem, which sends response data packets upstream via a public switched telephone network to a telephone remote access concentrator. Next, the telephone remote access concentrator sends the response data packets back to the appropriate host on the data network. When a cable modem used in a cable system is initialized, the cable modem establishes a communication link to a cable modem termination system via a cable network and, in telephony return data-over-cable systems, to a telephone return termination system via a public switched telephone network. As the cable modem is initialized, the cable modem initializes one or more downstream channels via the cable network. Also upon initialization, the cable modem receives a configuration file (a boot file) from a configuration server via a trivial file-transfer protocol (“TFTP”) exchange process.
The configuration file may include a plurality of configuration parameters encoded in a type-length-value format (“TLV”), for instance. The configuration file may comprise a plurality of Class-of-Service (“CoS”) and Quality-of-Service (“QoS”) parameters. The Class of Service parameters include, for example, maximum allowed data rates, minimum reserved data rate, maximum latency and a plurality of other parameters. The Quality of Service parameters include, for example, parameters defining delays expected to deliver data to a specific destination, a level of protection from unauthorized monitoring or modification of data, an expected residual error probability, a relative priority associated with data and a plurality of other parameters.
Upon a receipt of a configuration file, a cable modem may register with a cable modem termination system. To do that, the cable modem may send to the cable modem termination system a registration request message comprising a copy of the configuration file including a plurality of QoS and CoS parameters.
Similarly to a cable modem, a customer premise equipment entity obtains network access parameters such as an IP address of a network interface via which the customer premise equipment entity may send and receive data from a data network. Typically, a customer premise equipment entity receives an IP address from a network server such as a Dynamic Host Configuration Protocol server. Further, as is known in the art, when a network server provides an IP address for a customer premise equipment entity, the server typically leases that address for a predetermined period of time, and the customer premise equipment entity has to renew the lease prior to the lease's expiration. It is often desirable that a customer premise equipment entity receives the same IP address upon the lease renewal. However, when an original lease of a customer premise equipment entity expires during the time when the customer premise equipment entity is turned off, there is a very low probability that the customer premise entity receives the same IP address upon sending a lease renewal request to a designated network server.
Further, during a mass re-registration following a headend system failure, the network activity on network servers providing network services to customer premise equipment entities often exceeds acceptable loads, and many customer premise equipment entities may not be able to renew their leases for a longer time. Additionally, when many customer premise equipment entities try to acquire network services at the same time, the upstream bandwidth usage may exceed acceptable limits.
Further, as is known in the art, there are two types of IP addresses that are assigned to network devices. A public access IP address is typically used to reach network devices such as mail servers located on other networks, and may not be used to access public networks. Typically, cable modems are assigned private access IP addresses and may not access network devices on public networks. However, in some applications, it would be desirable to provide a cable modem with an ability to access network devices or servers on public networks. Further, it is desirable to develop a system and method that would allow for longer retention of IP address leases at a customer premise equipment entity and reduction of a traffic load on a network server providing services to many customer premise equipment entities.